Abstract:
This report specifies a design that will resolve the leaking roof problem that New Flyer has been experiencing on their 40-foot transit bus model. The problem was found to result from large deformation of the fiberglass roof panel when it was subjected to thermal cycling. The proposed composite design incorporates the use of a vinyl ester matrix with a two-ply 1808 e-glass fiber cloth. The expected coefficient of thermal expansion of this composite is 8-12 μm/m°C. The model used to predict this coefficient of thermal expansion of the composite was verified using a two-ply 1808 polyester resin composite and the currently employed fiber and resin configuration. Along with these changes to the composite composition, the use of Sika booster for all three beads of Sika polyurethane adhesives was suggested. This report shows that not only do these modifications resolve the issue of a leaking roof, but also yield a more rigid roof by increasing the flexural strength and elastic modulus of the composite by nearly 150%. It is also recommended within this report to incorporate composite drip rails within the roof shell, as this will lead to cost savings and decreased labour time. There is no substantial change from the current budget in overall manufacturing or assembly costs for the proposed solution, which falls well within the budget allotted by New Flyer.
